Time Harmonics Investigation of Stator and Rotor Currents of a Dedicated Induction Machine

Condition monitoring of electric machines is ofincreasing importance. The continuous assessment of themachine performance allows to schedule appropriatelymaintenance operations, thus increasing machineoperating life and reducing repair cost. The input currentspectrum is a wide spread procedure for non-invasive diagnosisof induction machines.Information on rotor variables are available only bycomputation, typically by FEM. Experimental results aredifficult to achieve: specific sensors must be mounted on therotor to detect currents or flux density.In this paper a dedicated machine and experimental set-up,developed at IEN, was used, that allows to detect single barcurrents through sensors positioned on the rotor bars. So doing itis possible to compute both rotor phase currents and space vectorspectra.The main phenomena, that introduce waveform distortion, arebriefly recalled and the corresponding spectrum lines for bothstator and rotor currents are reported and analyzed in thispaper